Distinguish async vs sync database drivers in Python DB spans (FastAPI / SQLAlchemy / asyncpg)

### Problem Statement

In Sentry Performance for Python async applications (FastAPI + SQLAlchemy async), all database spans appear generically as:

op: db
description: SELECT ...

There is currently no visible way in the UI or span attributes to determine whether the underlying database driver is:

async (e.g., asyncpg, SQLAlchemy asyncio), or

sync (e.g., psycopg2, synchronous SQLAlchemy)

This makes it difficult to verify that async applications are using non-blocking database drivers and not accidentally introducing sync DB calls inside async endpoints.

### Solution Brainstorm

_No response_

### Product Area

Insights